The invention relates to small scale, force activated, electricity generation, storage and supply apparatus. More specifically, the invention relates to systems for converting mechanical force into electrical energy in a form which can be efficiently utilized for powering small scale electrical apparatuses.
The term piezoelectric refers to a class of materials which exhibit the generation of an electrical charge when subjected to an applied force that produces stress or otherwise induces strain in the piezoelectric material.
One common type of piezoelectric device is a pressure transducer. Such piezoelectric pressure transducers typically are exposed to a fluid medium which exerts pressure directly or indirectly upon a diaphragm. The diaphragm is mechanically coupled to a piezoelectric element in a manner that applies a force thereto. The applied force generates a stress and related strain in the piezoelectric material. The piezoelectric element or elements respond to the applied force and strain by generating an electrical charge. The electrical charge is directed to poles of the piezoelectric element which have electrical leads connected thereto. Electrical circuitry detects this generated electric charge and derives an electric signal representative of the pressure within the fluid medium.
One attribute of piezoelectric sensors and other similar piezoelectric devices is that the amount of electrical charge is typically very low. This small amount of electrical charge can be easily adapted to in the context of sensors because the flow of charge can be highly impeded using the sensor detection circuitry. The high impedance allows a small charge to produce a detectable voltage and provide a high degree of sensitivity.
Even though piezoelectric sensors have been very successful, there has remained a substantial problem in generating a useful and efficient amount of electrical charge from piezoelectric generators for use as sources of electrical power. This limitation has severely restricted the potential applications for such devices, particularly when the devices are passive relative to any other source of electricity. In prior devices, the small amount of charge has effectively been lost in the generator and associated circuitry thus severely restricting the utility to applications having extremely low power requirements.
There remains a need in this technical art for piezoelectric power supplies which can efficiently generate useful amounts of electricity for operating small scale electrical devices. In particular, there is a need for completely passive or, otherwise unpowered devices that can be used to generate electricity for relatively small scale electrical devices. Such small scale piezoelectric generators may be particularly desirable where carried upon a person or small object or device needing only a small electrical consumption.
These and other objectives and considerations have been fully or partially addressed by the current invention, which is described in detail below. Some of the benefits and advantages of the current invention will be given in this description. Others will be apparent from the nature of the invention when considered in conjunction with the description given herein. Although effort is made to fully describe the invention and it""s various benefits, advantages and principals of operation; some of such information may not be evident or available at this time. In the future such may become evident or available after additional experience is gained using the invention. The best modes of the invention and various features and advantages now known are described herein.